Balancing of ring cutoff circuit for long and short lines



BALANCING 0F RING 'CUTOFF CIRCUIT FOR LONG AND SHORT LINES Filed Dec. 12, 1946 Oct. 25, 1949. BURGENER v 2,486.,1 1 1 INVENTOR. KARL l. BURGENER ATTORNEY Patented Oct. 25, 1949 UNITED STATES PATENT OFFICE BALANCING OF RING CUTOFF CIRCUIT FOR LONG AND SHORT LINES Application December 12, 1946, Serial No. 715,738

11 Claims.

The present invention relates to telephone systems in general, and more particularly to improved circuits for quickly cutting off the ringing current when th called subscriber answers.

An object of the invention is to provide new and novel circuit arrangements for quickly disconnecting ringing current from subscribers lines of different characteristics in response to such subscribers answering.

Another object of the invention is to provide improved balancing circuit arrangement-s for controlling the operations of a differential ring cut-off relay which connects and disconnects ringing current from the subscribers lines.

A feature of the present invention relates to means for including or excluding compensating resistances in the balancing winding of the differential ring cut-off relay to compensate for different line characteristics when the other winding of th ring cut-off relay is bridged across the called subscribers line during the ringing period.

Another feature relates to the manner in which the compensating resistances are included and excluded in the following circuit of the ring outoff relay in accordance with different line characteristics of the called lines.

The connector switch has access to lines having different characteristics, such as long and short lines and lines with a few or a large number of ringers thereon. Lin-es having short line characteristics are marked by two methods. In order to maintain a balance in the differential relay during connections to the different types of lines, a resistance is included or excluded from the knock down winding of the ring cut-off relay dependent upon the marked condition or an absence of the marked condition of the line or groups of lines being called. Such lines may be marked on a line or a group basis. If the lines are marked on a line basis, then a fourth wiper and an individual bank contact connected to ground is used to shunt the resistance when a stronger balancing circuit is required for the differential ring cut-off relay. If the lines are marked on a group basis, then normal post springs operated on a particular level close a circuit to exclude the resistance to strengthen the balancing circuit for the ring outoff relay.

The invention is illustrated herein as applied to the well known Strowger step by step system, although it may conceivably be useful in other systems.

The invention will be described more in detail hereinafter, reference being made to the accompanying drawing, which shows by means of the usual circuit diagrams sufficient of the apparatus of an automatic telephone system to enable the invention to be explained and understood.

Referring to the drawing, the reference character C indicates a connector switch of the well known Strowger type such as has been hereinbefore mentioned, a single subscribers station A, and a party line B, containing subscribers C, D, E and F. This-connector may be assumed to be one of a group of connectors having access to one hundred subscribers lines, conforming to the customary practice in the Strowger system. This connector is of the type described in Patent 2,040,153 of May 12, 1936, to Seth Peterson, but modified to contain the present invention.

Two different types of lines, having different line characteristics, to which connector C may have access are shown at the right of the drawing and comprises conductors 10, H and 10 and l l. The lines are multipled in the banks of the connectors, such as C, so as to provide for incoming calls. Outgoing calls are made by means of the rotary line switch RL, which has access to selectors. These features are all well understood and need not be explained in detail.

The general operation of the connector C is well known, but nevertheless will be briefly described preliminary to explaining the operation of applicants aforementioned invention.

Assuming that connector C has been seized by a selector, the calling line will be extended to trunk conductors I3 and I5, which results in the energization of line relay 3, followed by the energization of release relay 4. The latter grounds release trunk conductor [4 so as to provide a holding circuit for the preceding switches.

The calling subscriber then dials the tens digit in the number, which causes line relay 3 to deenergize momentarily a number of times, sending impulses to vertical magnet l0, which steps up wipers i6, I1 and It until they stand opposite the level in which the called line is terminated. Relay 5 being slow to release is in series with vertical magnet l0 and cooperates with off-normal springs On to transfer the impulse circuit to the rotary magnet H at the end of the vertical I operation.

The calling subscriber can now dial the last or units digit of the called number. Line relay 3 operates as before, but now send-s a series of impulses to rotary magnet II. Accordingly, the wipers I6, i1 and I8 are rotated step by step until they come to rest on the called line terminals.

. It will be assumed that the called line is the line 3 of station A and that the wipers are positioned on contacts 20, 2| and 22.

Slow to release relay 8 is connected in parallel with rotary magnet l l and is in operated position during the rotary movement. At armature 24, relay 8 connects test wiper l! with busy relay 7, which in turn opens the rotary magnet circuit at its armature 27. Since the busy relay 1 is liable to be operated during the rotary movement of test Wiper I1 engaging grounded contacts of busy lines, relay 8 maintains the rotary magnet circuit closed by armature 25.

Assuming that the rotary movement has just ceased, with the connector wipers positioned on the called line, relay 8 will remain operated for an instant and hold the test wiper ii in connection with busy relay l. If the called line is busy there will be a ground potential on test contact 2! and relay 1 will energize. When relay 8 falls back a locking circuit is established for relay 1 in an obvious manner. Relay l holds open the rotary magnet circuit so as to prevent the connector from being moved off the busy called line by further operation of the dial, and also applies a source of busy tone current to the calling line.

Assuming that now the called line is idle when connected with, busy relay 7 will not pull up because test wiper l? finds no ground on test contact 2!. Then when relay 8 falls back a circuit is completed for energizing switch through relay 9, extended from the grounded conductor 14, by way of contacts 23 of busy relay 1, the lower winding of relay 9, contacts 24 of relay 6, test wiper ll, test contact 2|, switch over relay 4d of. line, switch RL, and. the rotary magnet 4! of the said line switch to battery. Relay 9 pulls up in series with the switch over relay 48, the latter which performs usual well known functions. Relay 9' is slightly slow to operate, to give time for the operation of the switch-over relay. As the armature of relay 9. is attracted, the pair of springs represented by armature 29 and its working contact are closed first, thus completing an energizing circuit for the upper locking winding. The two windings then cooperate in fully operating the relay and thus all the springs of the relay are actuated. Armature 3|} grounds the test wiper ll, armature 31 opens the circuit to rotary magnet H, and the upper armature 36 and lower armature 43 connect up line wipers l6 and I8 respectively.

Before continuing with the further operations of the connector, a discussion of the applicants invention, and its operation within the connector will be expounded.

As release relay 4 is energized, its armature 45 grounds conductor M and the lower winding of differential ring cut-ofi relay 6 is energized, a circuit may be traced from the battery of the lower winding through armature 42 to conductor 44 and to ground through armature d5. Differential ring cut-01f relay 6 now operates its respective armatures 34, 35, 46 and 4?. Relay 6 is so constructed as being both slow to operate and slow to release and thus not affected when ringing current traverses its upper winding. An additional holding circuit through the lower wind ing isprovided for relay 6, from battery through armature 35, through series connected resistances 32 and 33 and to ground at armature 45. If a number of lines are found to contain. similar characteristics, they may be grouped on. the same level or groups of levels. Normal post springs 37 are used to mark such lines on a group basis. Normal post springs 31 are actuated when the connector is operated to such levels, thereby shunting resistance 33. The holding circuit through the lower winding of relay 6 may be traced from battery through armature 35 through resistance 32 and to ground through normal post springs 3'7. In case other lines having difierent characteristics are promiscuously interspersed on any one level or levels, then certain of these lines having corresponding specific line characteristics, such as short lines, would have to be marked on a line basis. In order to mark such. lines an individual bank contact, such as contact 39, is provided and connected to ground. The other lines, having long line characteristics, also have individual bank contacts but such contacts are not connected to ground. In case the connector switch has been operated to connect with a line marked on an individual line basis, then. Wiper 38 of the connector engages a grounded contact, such as 39. The holding circuit for the lower winding of relay 6 may then be traced from battery through armature 35, resistance 32 and through wiper 38 to contact 39 to ground. Though. the drawing illustrates the group marking arrangement comprising normal post springs Bl and conductor X, and the individual line marking arrangement comprising contact 3Q, wiper 38, and conductor Y, it is. to be understood that a connector would normally contain only one of such marking arrangements, with the circuit being permanently made at point P.

After operation of switch through relay 9, ringing current is. now projected through armature 46 and out over the called line and back into the upper winding of relay 6 to battery. As relay 6' is specially constructed, the alternating ringing current will not affect it. The called party, upon answering, completes a direct current path over the line and through the upper winding of relay 6. As the two windings of relay B oppose one another, and their respective circuit, resistances are proportionately equal, the passage of direct currentthrough the upper winding builds an opposing flux, and thus neutralizes the effect of the lower winding, and knocks down the relay when the call is answered- Relay 5, upon restoring at armature 46 and armature 34, completes the talking connection between. the called party and the calling party.

As hereinbefore stated, a connector would normally contain only one of the marking arrangements. using either the conductor X and normal post. springs 37, or the conductor Y, wiper 38 and contact 39-. If desired, both marking arrangements may be used in the same switch.

In prior systems, the usualv practice was to operate the ring cut-oifrelay when. the called party answers.v Inv the present invention, the ring cut-off relay is a difierentially wound relay having two. windings one of which is used to operate the relay before the ringing operation. This same winding is converted into a holding winding for holding the relay operated during the ringing operation. The other winding, which is wound to oppose the first winding, is connected to lines having different characteristics. In order to create. a balance between these two windings, the circuit arrangements above described, have been provided to change the resistance in the holding, or balancing first winding circuit to approximately equal to the resistance of the line circuit including. the second winding. ,With the resistance in the two circuits, including the two windings, approximately equal, the relay will be more sensitive, and its function will be faster and more positive, with the result that ringing current will be quickly disconnected from the called line.

Having described my invention, what is considered to be new and is desired to be protected by Letters Patent will be set forth in the subjoining claims.

What is claimed is:

1. In a telephone system, subscriber lines having long line characteristics, other subscriber lines having short line characteristics, a connector switch having access to said lines, a differential ring cut-off relay in said switch having two windings, means responsive to the seizure of said switch for operating said relay, means for operating said switch to connect with a called one of said lines, a circuit for holding said relay operated over one of its windings after said connection, means for bridging the other winding of said relay across said called line and for connecting ringing current to the called line, means for energizing said other winding of said relay in response to the called subscriber answering to restore said relay to disconnect'ringing current, compensating resistances in said connector switch, and means for including all of said resistances or only a portion of said resistances in said holding circuit dependent upon the characteristics of said called line for balancing the current flow through said two windings of said differential ring cut-off relay to assist in the restoration of said relay when the called subscriber answers.

2. In a telephone system, subscriber lines having long line characteristics, other subscriber lines having short line characteristics, means including an automatic switch for interconnecting said lines, a differential ring cut-off relay in said automatic switch and having opposing windings, means for operating said relay over one of its windings in response to a calling one of said lines being connected to said automatic switch, means for thereafter bridging the other winding of said relay across a called one of said lines and for connecting ringing current to the called line, a circuit for holding said relay operated over said one winding during the ringing operation, compensating resistances, means for including all of said resistances or only a portion of said resistances in said holding circuit dependent upon the characteristics of said called line, and means for energizing said other winding in response to the called subscriber answering to restore said relay and disconnect ringing circuit.

3. In a telephone system, subscriber lines having long line characteristics, other subscriber lines having short line characteristics, a connector switch having access to said lines, a ring cut-off relay in said switch, means responsive to the seizure of said switch for operating said relay, means for operating said switch to connect with a called one of said lines, compensating resistances in said switch, means for holding said relay operated after connection of said switch to said called line over a circuit including a winding of said relay and said resistances in case said called line has long line characteristics, and means for holding said relay operated after connection of said switch to said called line over a circuit including said winding and only a portion of said resistances in case said called line has short line characteristics.

4. In a telephone system, subscriber lines having long line characteristics, other subscriber lines having short line characteristics, means including an automatic switch for interconnecting said lines, a signaling source, a resistance, a differentially wound ring cut-ofi relay in said automatic switch and having two windings, a balancing circuit including one winding of said relay, means for operating said relay in response to a calling one of said lines being connected to said automatic switch, means for connecting said signal source to a called one of said lines through the other winding of said relay to signal a station on said called line, and for connecting all or only a portion of said resistance in series with said balancing circuit dependent upon the characteristics of the called line connected to and to compensate for the difierent characteristics of said lines.

5. In a telephone system, subscriber lines having long line characteristics, other subscriber lines having short line characteristics, means including an automatic switch for interconnecting said lines, a resistance, a differentially wound ring cutofi relay in said automatic switch and having two windings, said relay operated in response to a calling one of said lines being connected to said automatic switch, a balancing circuit including one winding of said relay, means for connecting said signal source to a called one of said lines through the other winding of said relay to signal a station on said called line, and means for connecting all of said resistance in series with said balancing circuit in case said called line has long line characteristics.

6. In a telephone system, subscriber lines having long line characteristics, other subscriber lines having short line characteristics, means including an automatic switch for interconnecting said lines, a signaling source, a resistance, a differentially wound ring cut-01f relay in said automatic switch and having two windings, said relay operated in response to a calling one of said lines being connected to said automatic switch, a balancing circuit including one winding of said relay, means for connecting said signal source to a called one of said lines through the other winding of said relay to signal a station on said called line, and means for connecting only a portion of said resistance in series with said balancing circuit in case said called line has short line characteristics.

7. In a telephone system, subscriber lines having long line characteristics, other subscriber lines having short line characteristics, means including an automatic switch for interconnecting said lines, a signaling source, a diirerentially wound ring cut-ofi relay in said automatic switch and having two windings, said relay operated in response to calling one of said lines being connected to said automatic switch, a balancing circuit including one winding of said relay, a resistance corresponding to said long lines characteristics, a portion of said resistance corresponding to said short lines characteristics, means for connecting said signalling source to a called one of said lines through the other winding of said relay to signal a party on said called line, and for connecting said resistance in series with said balancing circuit in case said one called line is a long line or for connecting only said portion of said resistance in series with said balancing circuit in case said one called line is a short line, said means also providing the proper power in said balancing circuit winding for neutralizing the power developed in the other winding of said relay when the subscriber answers, said neu- '1' tralization causing the release of said relay to disconnect said signal. source.

8.. In a telephone system, a-group ofsubscriber lines all having the same predetermined line characteristics, other subscriber lines having different line characteristics, a connector switch for connecting with a called one of said subscriber lines, a diiTerential ring cut-oil relay in said switch having two windings, means for operating said relay over one of said windings, means for bridging the other winding across said called line and for connecting ringing current to said called line, compensating resistances in said switch, a holding circuit for said relay normally including said resistances and said one winding in series, and marking means in said switch operative in case said called line is included in said group of subscriber lines for excluding. a portion of said resistances from said holding circuit.

9-. In a telephone system, subscriber lines having predetermined line-characteristics, other subscriber lines having different line characteristics, marking means individual to each of said first subscriber lines having said predetermined line characteristics, a connector switch for connecting with a called one of said lines, a differential ring cut-ofi relay in said switch having two windings, means for operating said relay over one of said windings, means for bridging the other of said windings across said called line and for connecting ringing current to said called line, compensating resistances in saidswitch, a holding circuit for said relay normally including said resistances and said one winding in series, and circuit means including the marking means individual. to. said called line for excluding a por tion of said resistances from said holding circuit.

10. In. a telephone system, subscriber lines all having the same predeterminedcharacteristics, agroup of subscriber lines also having the same predetermined characteristics, other subscriber lines having different line characteristics, a connector switch for connecting with a called one of said lines, a differential ring cut-off relay in said switch having two windings, means for operating-saidv relay over one of said windings, means for bridging the other. of said windings across said. called line. and for connectingv ring.- ing. current tov said called. line, compensating resistances in said connector switch, a holding circuit for said relay normally including. said resistances and said, one winding in series, individual marking means for each of said first subscriber lines all having the same predetermined characteristics, a circuit means including said individual marking means for excluding a portion of said resistances from said holding circuit when said. called line. is one of said first subscriber lines, a common marking. means for said. group-of subscriber lines having the same predetermined characteristics, and circuit means including said common marking means for excluding a portion of said resistances from said holding circuit when said called line is one of said group of subscriber lines.

11. ha signaling system, lines having different resistance characteristics, means for selectively extending calls from and to said lines, a signaling potential, means for automatically connecting said signaling potential to a called one of said lines, a relay operated in response to the extension of a call from a calling line to prepare a circuit for connecting said signaling. potential to said called line, a holding circuit completed in response to the operation of said relay for holding said relay operated during the signaling period, and means. for automatically changing the resistance in said holding circuit to approximately match the resistance characteristics of said called line in'response to the extension of said call to said called line.

KARL L. BURGENER.

REFERENCES CITED UNITED STATES PATENTS Name Date Burgener Nov. 12, 1946 Number 

